2points
what causes water molecules to stick together in liquid water?
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a. attractive forces called hydrogen bonds
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b. magnetic forces in our solar system
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c. expanding molecules in freezing temperatures
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d. gaseous molecules called water vapor
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A. Attractive forces called hydrogen bonds

Explanation:

A. Attractive forces called hydrogen bonds

Explanation:

Liquid water contains water molecules. The attractive forces between the water molecules is called HYDROGEN BONDING.

Hydrogen bonding is the intermolecular forces which exists between h atom and the highly electronegative atoms like N, O, F.

For example  

It is a polar covalent bond.  

It has a strong intermolecular forces.

Its strength is more than that of the London dispersion forces

It is also called as a dipole –dipole forces.

Dipole –dipole forces is the forces which exist between the polar molecules.

The electronegative values of H is 2.1

F is 4.0

O is 3.5 and

N is 3.0

∆E value of HF Hydrogen  bond  is 4.0 - 2.1 = 1.9

∆E value of Hydrogen bond is 3.5 - 2.1 = 1.4

∆E value of Hydrogen bond is 3.0 - 2.1 = 0.9

∆E value between 0.5 to 1.7 is a polar covalent bond

Hence Hydrogen bond is a bond between polar molecules and also comes under the category of dipole-dipole forces.

out of these options:

ability to burn paper

pure sodium reacting violently with water

the boiling point of water

helium does not tend to react with anything

i would say this is a physical property:

helium does not tend to react with anything

why? :

i said helium does not tend to react with anything because well, it reacts to ! but ability to burn paper, pure sodium reacting violently with water, & the boiling point of water are chemical or

physical properties: the properties of a substance that can be observed without changing the chemical makeup of the substance

chemical properties: properties of a substance relating to the chemical nature and reactivity of the substance

"the periodic table is arranged in order of atomic number."